More “fast radio bursts" – bright, short-lived pulses of radio waves that come from across the universe – have been detected by astronomers. The bursts, which originate from a distant galaxy that's 1.5 billion light years away from Earth, repeated 13 times, a new study reports.

This is only the second time that repeating fast radio bursts have been discovered.

“Until now, there was only one known repeating fast radio burst," said Ingrid Stairs, an astrophysicist at the University of British Columbia. "Knowing that there is another suggests that there could be more out there. And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles – where they’re from and what causes them."

The repeating fast radio burst was detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a radio telescope designed and built by several groups of Canadian scientists.

According to National Geographic, each radio burst lasts just thousandths of a second, and they all appear to be coming from far outside our home galaxy, the Milky Way.

Are they natural "sounds," or something else?

The BBC reports that there are a number of theories about what could be causing the bursts.

Theories include a neutron star with a very strong magnetic field that is spinning very rapidly, two neutron stars merging together, and, among a minority of observers, some form of alien spaceship, the BBC said.

Indeed, some astronomers have considered the idea that these bursts could be signals from intelligent aliens, Science News reported. Whatever their source, scientists think many more sources of repeating bursts will be detected in the future.